Method and apparatus for supercritical processing of multiple workpieces

ABSTRACT

An apparatus for supercritical processing of multiple workpieces comprises a transfer module, first and second supercritical processing modules, and a robot. The transfer module includes an entrance. The first and second supercritical processing modules are coupled to the transfer module. The robot is preferably located with the transfer module. In operation, the robot transfers a first workpiece from the entrance of the transfer module to the first supercritical processing module. The robot then transfers a second workpiece from the entrance to the second supercritical processing module. After the workpieces have been processed, the robot returns the first and second workpieces to the entrance of the transfer module. Alternatively, the apparatus includes additional supercritical processing modules coupled to the transfer module.

RELATED APPLICATIONS

This patent application is a divisional application of the co-pendingU.S. pat. application Ser. No. 09/704,642, filed Nov. 1, 2000, andtitled “METHOD AND APPARATUS FOR SUPERCRITICAL PROCESSING OF MULTIPLEWORKPIECES,” which claims priority from U.S. Provisional Pat.application Ser. No. 60/163,121, filed Nov. 2, 1999, and titled “A HIGHTHROUGHPUT CLUSTER TOOL FOR CLEANING SEMICONDUCTOR DEVICES USINGSUPERCRITICAL CO₂.” The U.S. Pat. application Ser. No. 09/704,642, filedNov. 1, 2000, and titled “METHOD AND APPARATUS FOR SUPERCRITICALPROCESSING OF A WORKPIECE,” is hereby incorporated by reference.

FIELD OF THE INVENTION

This invention relates to the field of supercritical processing. Moreparticularly, this invention relates to the field of supercriticalprocessing where multiple workpieces are processed simultaneously.

BACKGROUND OF THE INVENTION

Semiconductor fabrication uses photoresist in ion implantation, etching,and other processing steps. In the ion implantation steps, thephotoresist masks areas of a semiconductor substrate that are notimplanted with a dopant. In the etching steps, the photoresist masksareas of the semiconductor substrate that are not etched. Examples ofthe other processing steps include using the photoresist as a blanketprotective coating of a processed wafer or the blanket protectivecoating of a MEMS (micro electro-mechanical system) device. Followingthe ion implantation steps, the photoresist exhibits a hard outer crustcovering a jelly-like core. The hard outer crust leads to difficultiesin a photoresist removal. Following the etching steps, remainingphotoresist exhibits a hardened character that leads to difficulties inthe photoresist removal. Following the etching steps, residue(photoresist residue mixed with etch residue) coats sidewalls of etchfeatures. Depending on a type of etching step and material etched, thephotoresist residue mixed with the etch residue presents a challengingremoval problem since the photoresist residue mixed with the etchresidue often strongly bond to the sidewalls of the etch features.

Typically, in the prior art, the photoresist and the residue are removedby plasma ashing in an O₂ plasma followed by cleaning in a wet-cleanbath. A semiconductor etching and metallization process of the prior artis illustrated in block diagram format in FIG. 1. The semiconductoretching and metallization process 10 includes a photoresist applicationstep 12, a photoresist exposure step 14, a photoresist development step16, a dielectric etch step 18, an ashing step 20, a wet cleaning step22, and a metal deposition step 24. In the photoresist application step12, the photoresist is applied to a wafer having an exposed oxide layer.In the photoresist exposure step 14, the photoresist is exposed to lightwhich is partially blocked by a mask.

Depending upon whether the photoresist is a positive or negativephotoresist, either exposed photoresist or non-exposed photoresist,respectively, is removed in the photoresist development step 16 leavinga exposed pattern on the oxide layer. In the dielectric etch step 18,the exposed pattern on the oxide layer is etched in an RIE (reactive ionetch) process which etches the exposed pattern into the oxide layer,forming an etched pattern, while also partially etching the photoresist.This produces the residue which coats the sidewalls of the etch featureswhile also hardening the photoresist. In the ashing step 20, the O₂plasma oxidizes and partially removes the photoresist and the residue.In the wet cleaning step 22, remaining photoresist and residue iscleaned in the wet-clean bath.

In the metal deposition step 24, a metal layer is deposited on the waferfilling the etched pattern and also covering non-etched regions. Insubsequent processing, at least part of the metal covering thenon-etched regions is removed in order to form a circuit.

Nishikawa et al. in U.S. Pat. No. 4,944,837, issued on Jul. 31, 1990,recite a prior art method of removing a resist using liquidized orsupercritical gas. A substrate with the resist is placed into a pressurevessel, which also contains the liquidized or supercritical gas. After apredetermined time lapse, the liquidized or supercritical gas is rapidlyexpanded, which removes the resist.

Nishikawa et al. teach that supercritical CO₂ can be used as a developerfor photoresist. A substrate with a photoresist layer is exposed in apattern to light, thus forming a latent image. The substrate with thephotoresist and the latent image is placed in a supercritical CO₂ bathfor 30 minutes. The supercritical CO₂ is then condensed leaving thepattern of the photoresist. Nishikawa et al. further teach that 0.5% byweight of methyl isobutyl ketone (MIBK) can be added to thesupercritical CO₂, which increases an effectiveness of the supercriticalCO₂ and, thus, reduces a development time from the 30 minutes to 5minutes.

Nishikawa et al. also teach that a photoresist can be removed using thesupercritical CO₂ and 7% by weight of the MIBK. The substrate with thephotoresist is placed in the supercritical CO₂ and the MIBK for 30-45minutes. Upon condensing the supercritical CO₂, the photoresist has beenremoved.

The methods taught by Nishikawa et al. are inappropriate for asemiconductor fabrication line for a number of reasons. Rapidlyexpanding a liquidized or supercritical gas to remove a photoresist froma substrate creates a potential for breakage of the substrate. Aphotoresist development process which takes 30 minutes is tooinefficient. A photoresist development or removal process which usesMIBK is not preferred because MIBK is toxic and because MIBK is usedonly when a more suitable choice is unavailable.

Smith, Jr. et al. in U.S. Pat. No. 5,377,705, issued on Jan. 3, 1995,teach a system for cleaning contaminants from a workpiece. Thecontaminants include organic, particulate, and ionic contaminants. Thesystem includes a pressurizable cleaning vessel, a liquid CO₂ storagecontainer, a pump, a solvent delivery system, a separator, a condenser,and various valves. The pump transfers CO₂ gas and solvent to thecleaning vessel and pressurizes the CO₂ gas to supercritical CO₂. Thesupercritical CO₂ and the solvent remove the contaminants from theworkpiece. A valve allows some of the supercritical CO₂ and the solventto bleed from the cleaning vessel while the pump replenishes thesupercritical CO₂ and the solvent. The separator separates the solventfrom the supercritical CO₂. The condenser condenses the CO₂ to liquidCO₂ so that the liquid CO₂ storage container can be replenished.

Employing a system such as taught by Smith, Jr. et al. for removingphotoresist and residue presents a number of difficulties. Thepressurizable cleaning vessel is not configured appropriately forsemiconductor substrate handling. It is inefficient to bleed thesupercritical CO₂ and the solvent during cleaning. Such a system is notreadily adaptable to throughput requirements of a semiconductorfabrication line. Such a system is not conducive to safe semiconductorsubstrate handling, which is crucial in a semiconductor fabricationline. Such a system is not economical for semiconductor substrateprocessing.

What is needed is a method of developing photoresist using supercriticalcarbon dioxide appropriate for a semiconductor fabrication line.

What is needed is a method of removing photoresist using supercriticalcarbon dioxide appropriate for a semiconductor fabrication line.

What is needed is a supercritical processing system which is configuredfor handling semiconductor substrates.

What is needed is a supercritical processing system in whichsupercritical CO₂ and solvent are not necessarily bled from a processingchamber in order to create a fluid flow within the processing chamber.

What is needed is a supercritical processing system which meetsthroughput requirements of a semiconductor fabrication line.

What is needed is a supercritical processing system which provides safesemiconductor substrate handling.

What is needed is a supercritical processing system which provideseconomical semiconductor substrate processing.

SUMMARY OF THE INVENTION

The present invention is an apparatus for supercritical processing ofmultiple workpieces. The apparatus includes a transfer module, first andsecond supercritical processing modules, and a robot. The transfermodule includes an entrance. The first and second supercriticalprocessing modules are coupled to the transfer module. The robot ispreferably located within the transfer module. In operation, the robottransfers a first workpiece from the entrance of the transfer module tothe first supercritical processing module. The robot then transfers asecond workpiece from the entrance to the second supercriticalprocessing module. After the workpieces have been processed, the robotreturns the first and second workpieces to the entrance of the transfermodule. Alternatively, the apparatus includes additional supercriticalprocessing modules coupled to the transfer module.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates, in block diagram format, a process flow for asemiconductor etching and metallization process of the prior art.

FIG. 2 illustrates, in block diagram format, a process flow for asemiconductor etching and metallization process of the presentinvention.

FIG. 3 illustrates, in block diagram format, a supercritical removalprocess of the present invention.

FIG. 4 illustrates the preferred supercritical processing system of thepresent invention.

FIG. 5 illustrates the preferred supercritical processing module of thepresent invention.

FIG. 6 illustrates a first alternative supercritical processing systemof the present invention.

FIG. 7 illustrates a second alternative supercritical processing systemof the present invention.

FIG. 8 illustrates a third alternative supercritical processing systemof the present invention.

FIG. 9 illustrates a fourth alternative supercritical processing systemof the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A semiconductor etch and metallization process of the present inventionis illustrated, as a block diagram, in FIG. 2. The semiconductor etchand metallization process 30 includes a photoresist application step 32,a photoresist exposure step 34, a photoresist development step 36, adielectric etch step 38, a supercritical removal process 40, and a metaldeposition step 42. In the photoresist application step 32, thephotoresist is applied to a wafer having an exposed oxide layer. In thephotoresist exposure step 34, the photoresist is exposed to light whichis partially blocked by a mask.

Depending upon whether the photoresist is a positive or negativephotoresist, either exposed photoresist or non-exposed photoresist,respectively, is removed in the photoresist development step 36 leavinga exposed pattern on the oxide layer. In the dielectric etch step 38,the exposed pattern on the oxide layer is preferably etched in an RIE(reactive ion etch) process which etches the exposed pattern into theoxide layer while also partially etching the photoresist. This producesthe residue which coats the sidewalls of the etch features while alsohardening the photoresist.

In the supercritical removal process 40, supercritical carbon dioxideand a solvent are used to remove the photoresist and the residue. In themetal deposition step 42, a metal layer is deposited on the waferfilling the etched pattern and also covering non-etched regions. Insubsequent processing, at least part of the metal covering thenon-etched regions is removed in order to form a circuit.

The supercritical removal process 40 of the present invention isillustrated, as a block diagram, in FIG. 3. The supercritical removalprocess 40 begins by placing the wafer, with the photoresist and theresidue on the wafer, within a pressure chamber and sealing the pressurechamber in a first process step 52. In a second process step 54, thepressure chamber is pressurized with carbon dioxide until the carbondioxide becomes the supercritical carbon dioxide (SCCO₂). In a thirdprocess step 56, the supercritical carbon dioxide carries a solvent intothe process chamber. In a fourth process step 58, the supercriticalcarbon dioxide and the solvent are maintained in contact with the waferuntil the photoresist and the residue are removed from the wafer. In thefourth process step 58, the solvent at least partially dissolves thephotoresist and the residue. In a fifth process step 60, the pressurechamber is partially exhausted. In a sixth process step 62, the wafer isrinsed. In a seventh process step 64, the supercritical removal process40 ends by depressurizing the pressure chamber and removing the wafer.

The supercritical removal process 40 is preferably implemented in asemiconductor fabrication line by the preferred supercritical processingsystem of the present invention, which is illustrated in FIG. 4. Thepreferred supercritical processing system 70 includes a transfer module72, first through fifth supercritical processing modules, 74-78, a robot80, and control electronics 82. The transfer module includes firstthrough fifth process ports, 84-88, and a transfer module entrance 90.The transfer module entrance 90 includes first and second hand-offstations, 92 and 94, and first and second entrance ports, 96 and 98.

The first through fifth supercritical processing modules, 74-78, arecoupled to the transfer module 72 via the first through fifth processports, 84-88, respectively. Preferably, the robot 80 is coupled to thetransfer module 72 at a center of the transfer module 72. The first andsecond hand-off stations, 92 and 94, are coupled to the transfer modulevia the first and second entrance ports, 96 and 98, respectively. Thecontrol electronics 82 are coupled to the transfer module 72.

Preferably, the transfer module 72 operates at atmospheric pressure.Alternatively, the transfer module 72 operates at a slight positivepressure relative to a surrounding environment where the slight positivepressure is produced by an inert gas injection arrangement. The inertgas injection arrangement injects an inert gas, such as Ar, CO₂, or N₂,into the transfer module 72. This assures a cleaner processingenvironment within the transfer module 72.

The robot 80 preferably includes a robot base 100, a robot arm 102, andan end effector 104. The robot base is coupled to the transfer module72. The robot arm 102 is preferably a two piece robot arm, which couplesthe end effector 104 to the robot base 100. The end effector 104 isconfigured to pick and place workpieces. Preferably, the end effector104 is configured to pick and place the wafer. Alternatively, the endeffector 104 is configured to pick and place a puck or other substrate.Alternatively, a dual arm robot replaces the robot 80, where the dualarm robot includes two arms and two end effectors.

The first through fifth supercritical processing modules, 74-78,preferably include first through fifth gate valves, 106-110,respectively. The first through fifth gate valves, 106-110, couple firstthrough fifth workpiece cavities, 112-116, of the first through fifthsupercritical processing modules, 74-78, respectively, to the firstthrough fifth process ports, 84-88.

Preferably, in operation, the robot 80 transfers a first workpiece 118from the first hand-off station 92 to the first supercritical processingmodule 74, where the supercritical removal process 40 is performed.Subsequently, the robot 80 transfers a second workpiece 120 from thefirst hand-off station 92 to the second supercritical processing module75, where the supercritical removal process 40 is performed. Further,the robot 80 transfers third through fifth workpieces (not shown) fromthe first hand-off station 92 to the third through fifth supercriticalprocessing modules, 76-78, respectively, where the supercritical removalprocess 40 is performed.

In subsequent operation, the robot 80 transfers the first workpiece fromthe first supercritical processing module 74 to the second hand-offstation 94. Further, the robot 80 transfers the second workpiece fromthe second supercritical processing module 75 to the second hand-offstation 94. Moreover, the robot 80 transfers the third through fifthworkpieces from the third through fifth supercritical processingmodules, 76-78, respectively, to the second hand-off station 94.

Preferably, the first workpiece 118, the second wafer 120, and the thirdthrough fifth workpieces are wafers. Preferably, the wafers are in afirst cassette at the first hand-off station 92 prior to supercriticalprocessing. Preferably, the wafers are placed by the robot 80 in asecond cassette at the second hand-off station 94 following thesupercritical processing. Alternatively, the wafers begin and end in thefirst cassette at the first hand-off station 92 along while a secondgroup of wafers begins and ends in the second cassette at the secondhand-off station 94.

It will be readily apparent to one skilled in the art that the secondhand-off station 94 can be eliminated or that additional hand-offstations can be added to the preferred supercritical processing system70. Further, it will be readily apparent to one skilled in the art thatthe preferred supercritical processing system 70 can be configured withless than the first through fifth supercritical processing modules,74-78, or more than the first through fifth supercritical processingmodules, 74-78. Moreover, it will be readily apparent to one skilled inthe art that the robot 80 can be replaced by a transfer mechanism whichis configured to transfer the first workpiece 118, the second workpiece120, and the third through fifth workpieces. Additionally, it will bereadily apparent to one skilled in the art that the first and secondcassettes can be front opening unified pods which employ a standardmechanical interface concept so that the wafers can be maintained in aclean environment separate from the surrounding environment.

The first supercritical processing module 74 of the present invention isillustrated in FIG. 5. The first supercritical processing module 74includes a carbon dioxide supply vessel 132, a carbon dioxide pump 134,the pressure chamber 136, a chemical supply vessel 138, a circulationpump 140, and an exhaust gas collection vessel 144. The carbon dioxidesupply vessel 132 is coupled to the pressure chamber 136 via the carbondioxide pump 134 and carbon dioxide piping 146. The carbon dioxidepiping 146 includes a carbon dioxide heater 148 located between thecarbon dioxide pump 134 and the pressure chamber 136. The pressurechamber 136 includes a pressure chamber heater 150. The circulation pump140 is located on a circulation line 152, which couples to the pressurechamber 136 at a circulation inlet 154 and at a circulation outlet 156.The chemical supply vessel 138 is coupled to the circulation line 152via a chemical supply line 158, which includes a first injection pump159. A rinse agent supply vessel 160 is coupled to the circulation line152 via a rinse supply line 162, which includes a second injection pump163. The exhaust gas collection vessel 144 is coupled to the pressurechamber 136 via exhaust gas piping 164.

The carbon dioxide supply vessel 132, the carbon dioxide pump 134, andthe carbon dioxide heater 148 form a carbon dioxide supply arrangement149. The chemical supply vessel 138, the first injection pump 159, therinse agent supply vessel 160, and the second injection pump 163 form achemical and rinse agent supply arrangement 165. Preferably, the carbondioxide supply arrangement 149, the chemical and rinse agent supplyarrangement 165, and the exhaust gas collection vessel 144 service thesecond through fifth supercritical processing modules, 75-78, (FIG. 3)as well as the first supercritical processing module 74. In other words,preferably, the first supercritical processing module 74 includes thecarbon dioxide supply arrangement 149, the chemical and rinse agentsupply arrangement 165, and the exhaust gas collection vessel 144 whilethe second through fifth supercritical processing modules, 75-78, sharethe carbon dioxide supply arrangement 149, the chemical and rinse agentsupply arrangement 165, and the exhaust gas collection vessel 144 of thefirst supercritical processing module 74.

It will be readily apparent to one skilled in the art that one or moreadditional carbon dioxide supply arrangements, one or more additionalchemical and rinse agent supply arrangements, or one or more additionalexhaust gas collection vessels can be provided to service the secondthrough fifth supercritical processing modules, 75-78. Further, it willbe readily apparent to one skilled in the art that the firstsupercritical processing module 74 includes valving, controlelectronics, filters, and utility hookups which are typical ofsupercritical fluid processing systems. Moreover, it will be readilyapparent to one skilled in the art that additional chemical supplyvessels could be coupled to the first injection pump 159 or that theadditional chemical supply vessels and additional injection pumps couldbe coupled to the circulation line 152.

Referring to FIGS. 3, 4, and 5, implementation of the supercriticalremoval method 40 begins with the first process step 52, in which thewafer, having the photoresist or the residue (or both the photoresistand the residue) is inserted through the first process port and placedin the first wafer cavity 112 of the pressure chamber 136 by the robot80 and, then, the pressure chamber 136 is sealed by closing the gatevalve 106. In the second process step 54, the pressure chamber 136 ispressurized by the carbon dioxide pump 134 with the carbon dioxide fromthe carbon dioxide supply vessel 132. During the second step 54, thecarbon dioxide is heated by the carbon dioxide heater 148 while thepressure chamber 136 is heated by the pressure chamber heater 150 toensure that a temperature of the carbon dioxide in the pressure chamber136 is above a critical temperature. The critical temperature for thecarbon dioxide is 31° C. Preferably, the temperature of the carbondioxide in the pressure chamber 136 is within a range of 45° C. to 75°C. Alternatively, the temperature of the carbon dioxide in the pressurechamber 136 is maintained within a range of from 31° C. to about 100° C.

Upon reaching initial supercritical conditions, the first injection pump159 pumps the solvent from the chemical supply vessel 138 into thepressure chamber 136 via the circulation line 152 while the carbondioxide pump further pressurizes the supercritical carbon dioxide in thethird process step 56. At a beginning of a solvent injection, thepressure in the pressure chamber 136 is about 1,100-1,200 psi. Once adesired amount of the solvent has been pumped into the pressure chamber136 and desired supercritical conditions are reached, the carbon dioxidepump 134 stops pressurizing the pressure chamber 136, the firstinjection pump 159 stops pumping the solvent into the pressure chamber136, and the circulation pump 140 begins circulating the supercriticalcarbon dioxide and the solvent in the fourth process step 58.Preferably, the pressure at this point is about 2,700-2,800 psi. Bycirculating the supercritical carbon dioxide and the solvent, thesupercritical carbon dioxide maintains the solvent in contact with thewafer. Additionally, by circulating the supercritical carbon dioxide andthe solvent, a fluid flow enhances removal of the photoresist and theresidue from the wafer.

Preferably, the wafer is held stationary in the pressure chamber 136during the fourth process step 58. Alternatively, the wafer is spunwithin the pressure chamber 136 during the fourth process step 58.

After the photoresist and the residue has been removed from the wafer,the pressure chamber 136 is partially depressurized by exhausting someof the supercritical carbon dioxide, the solvent, removed photoresist,and removed residue to the exhaust gas collection vessel 144 in order toreturn conditions in the pressure chamber 136 to near the initialsupercritical conditions in the fifth process step 60. Preferably, thepressure within the pressure chamber 136 is cycled at least once at thispoint by raising the pressure and then again partially exhausting thepressure chamber 136. This enhances a cleanliness within the pressurechamber 136. In the fifth process step 60, the pressure chamber ispreferably maintained above the critical temperature and above acritical pressure. The critical pressure for carbon dioxide is 1,070psi.

In the sixth process step 62, the second injection pump 163 pumps arinse agent from the rinse agent supply vessel 160 into the pressurechamber 136 via the circulation line while the carbon dioxide pump 134pressurizes the pressure chamber 136 to near the desired supercriticalconditions and, then, the circulation pump 140 circulates thesupercritical carbon dioxide and the rinse agent in order to rinse thewafer. Preferably, the rinse agent is selected from the group consistingof water, alcohol, acetone, and a mixture thereof. More preferably, therinse agent is the mixture of the alcohol and the water. Preferably, thealcohol is selected from the group consisting of isopropyl alcohol,ethanol, and other low molecular weight alcohols. More preferably, thealcohol is selected from the group consisting of the isopropyl alcoholand the ethanol. Most preferably, the alcohol is the ethanol.

Preferably, the wafer is held stationary in the pressure chamber 136during the sixth process step 62. Alternatively, the wafer is spunwithin the pressure chamber 136 during the sixth process step 62.

In the seventh process step 64, the pressure chamber 136 isdepressurized, by exhausting the pressure chamber 136 to the exhaust gascollection vessel 144, the gate valve 106 is opened, and the wafer isremoved from the pressure chamber 136 by the robot 80.

Alternative supercritical removal processes of the present invention aretaught in the following patent applications, all of which areincorporated in their entirety by reference: U.S. patent application(Attorney Docket No. SSI-00103), filed on Oct. 25, 2000; U.S. patentapplication Ser. No. 09/389,788, filed on Sep. 3, 1999; U.S. patentapplication Ser. No. 09/085,391, filed on May 27, 1998; and U.S.Provisional Patent Application No. 60/047,739, filed May 27, 1997.

A first alternative supercritical processing system of the presentinvention is illustrated in FIG. 6. The first alternative supercriticalprocessing system 170 adds first through fifth ante-chambers, 172-176,and first through fifth ante-chamber robots, 178-182, to the preferredsupercritical processing system 170. In operation, the first throughfifth ante-chambers, 172-176, operate from about atmospheric pressure tosome elevated pressure. This allows the first through fifth wafercavities, 112-116, to operate between the elevated pressure andsupercritical pressure and, thus, enhancing throughput. Alternatively,in the first alternative supercritical processing system 170, the firstthrough fifth ante-chamber robots, 178-182, are replaced with firstthrough fifth magnetically coupled mechanisms, or first through fifthhydraulically driven mechanisms, or first through fifth pneumaticallydriven mechanisms.

A second alternative supercritical processing system of the presentinvention of the present invention is illustrated in FIG. 7. The secondalternative supercritical processing system 190 replaces the first andsecond hand-off stations, 92 and 94, of the preferred supercriticalprocessing system 70 with first and second loadlocks, 192 and 194. Inoperation, the transfer module operates at a second elevated pressureand, thus, also enhances the throughput.

A third alternative supercritical processing system of the presentinvention of the present invention is illustrated in FIG. 8. The thirdalternative supercritical processing system 200 comprises an alternativetransfer module 202 and a robot track 204.

A fourth alternative supercritical processing system of the presentinvention is illustrated in FIG. 9. The fourth alternative supercriticalprocessing system 210 preferably replaces the third supercriticalprocessing module 76 of the preferred supercritical processing system 70with a third hand-off station 212 and adds a second transfer module 214,a second robot 216, and additional supercritical processing modules 218.In the fourth alternative supercritical processing system 210, the thirdhand-off station 212 couples the transfer module 72 to the secondtransfer module 214. The second robot 216 preferably resides in thesecond transfer module 214. The additional supercritical processingmodules 218 are coupled to the second transfer module 214. Thus, thefourth alternative supercritical processing system 210 allows for moresupercritical processing modules than the preferred supercriticalprocessing system 70.

A fifth alternative supercritical processing system of the presentinvention eliminates the transfer module 72 of the preferredsupercritical processing system 70. In the fifth alternativesupercritical processing system, the robot 80 is configured to moveworkpieces between the first and second hand-off stations, 92 and 94,and the first through fifth supercritical processing modules, 74-78,without benefitting from a covering effect provided by the transfermodule 72.

A sixth alternative supercritical processing system of the presentinvention adds an inspection station to the preferred supercriticalprocessing system 70. In the sixth alternative supercritical processingsystem, the first workpiece 118, the second workpiece 120, and the thirdthrough fifth workpieces are transferred to the inspection station priorto being transferred to the second hand-off station 94. At theinspection station, an inspection of the workpieces ensures that thephotoresist and the residue have been removed from the workpieces.Preferably, the inspection station uses spectroscopy to inspect theworkpieces.

A seventh alternative supercritical processing system of the presentinvention adds a front-end robot to the preferred supercriticalprocessing system 70. In the seventh alternative supercriticalprocessing system, the front-end robot resides outside of the entranceto the transfer module 72 and the first and second cassettes are locatedaway from the first and second hand-off stations, 92 and 94. Thefront-end robot is preferably configured to move the wafers from thefirst cassette to the first hand-off station 92 and is also preferablyconfigured to move the wafers from the second hand-off station 94 to thesecond cassette.

An eighth alternative supercritical processing system of the presentinvention adds a wafer orientation mechanism to the preferredsupercritical processing system 70. The wafer orientation mechanismorients the wafer according to a flat, a notch, or an other orientationindicator. Preferably, the wafer is oriented at the first hand-offstation 92. Alternatively, the wafer is oriented at the second hand-offstation 94.

A first alternative supercritical processing module of the presentinvention replaces the pressure chamber 136 and gate valve 106 with analternative pressure chamber. The alternative pressure chamber comprisesa chamber housing and a hydraulicly driven wafer platen. The chamberhousing comprises a cylindrical cavity which is open at its bottom. Thehydraulicly driven wafer platen is configured to seal against thechamber housing outside of the cylindrical cavity. In operation, thewafer is placed on the hydraulicly driven wafer platen. Then, thehydraulicly driven wafer platen moves upward and seals with the chamberhousing. Once the wafer has been processed the hydraulicly driven waferplaten is lowered and the wafer is taken away.

A second alternative supercritical processing module of the presentinvention places alternative inlets for the circulation line 152 toenter the wafer cavity 112 at a circumference of the wafer cavity 112and places an alternative outlet at a top center of the wafer cavity112. The alternative inlets are preferably configured to inject thesupercritical carbon dioxide in a plane defined by the wafer cavity 112.Preferably, the alternative inlets are angled with respect to a radiusof the wafer cavity 112 so that in operation the alternative inlets andthe alternative outlet create a vortex within the wafer cavity 112.

It will be readily apparent to one skilled in the art that other variousmodifications may be made to the preferred embodiment without departingfrom the spirit and scope of the invention as defined by the appendedclaims.

We claim:
 1. An apparatus for supercritical processing comprising: a. atransfer module having an entrance; b. an inert gas injectionarrangement coupled to the transfer module such that in operation theinert gas injection arrangement maintains a slight positive pressure inthe transfer module relative to a surrounding environment; c. a firstante-chamber coupled to the transfer module; d. a first supercriticalprocessing module coupled to the first ante-chamber; e. first means formoving a first semiconductor substrate between the first ante-chamberand the first supercritical processing module; f. a second ante-chambercoupled to the transfer module; g. a second supercritical processingmodule coupled to the second ante-chamber; h. second means for moving asecond semiconductor substrate between the second ante-chamber and thesecond supercritical processing module; and i. a transfer mechanismcoupled to the transfer module such that in operation the transfermechanism transfers the first and second semiconductor substratesbetween the first and second ante-chambers, respectively, and theentrance of the transfer module.
 2. The apparatus of claim 1, whereinthe inert gas injection arrangement is configured to insert an inert gasinto the transfer module.
 3. The apparatus of claim 2, wherein the inertgas is one of Ar, CO₂, and N₂.